Blender 2.8 pausing animation render
While you can't really pause it, the best practice is actually to output the individual frames as single images. That way, if the process needs to be stopped, you can resume it from the last rendered frame.



To do that, go to the Output menu, in the Output Properties tab, and set the File Format to an image format of your liking. I'd recommend that you also create a dedicated temporary folder to house the raw frames, and instruct Blender to output the images there.

Once all the frames have been rendered, you can proceed to converting them to a video format. To do so, open a new instance of Blender and, in the Video Sequencer editor, click Add > Image/Sequence then select the previously rendered frames. Set the animation playback's start/end frames to match those of your image strip. If you want to, in the dropdown menu in the top bar, select Sequencer/Preview and check if the animation is in order. 



Finally, in the Output Properties tab, select a video format, a suitable Output location and click Render Animation. Blender will then convert the image strip into a video.